My optima alarm sometimes goes off in the daytime when i am at home & the alarm is not set, also it does the same at night occasionally, after both instances, the tamper light indicator is lit, what could be the problem, it has worked flawlessly for years!
Tamper fault cold be a numbers of things.
Have a look at this link
http://ukpanels.com/forum1/showthread.php?tid=237
You can download the full document about tamper faults